The subject invention is directed toward the art of plastic forming and, more particularly, to a method of forming strip-like products from thermoplastic materials.
The invention is especially suited for forming trim strips and decorative strip components for vehicle bodies and will be described with particular reference thereto; however, as will become apparent, the invention is capable of broader application and could be used for forming a variety of strip-like products from thermoplastic materials.
Decorative and protective trim strips formed from thermoplastic materials are in widespread use in the automotive industry. The strips have been formed by both injection molding and extrusion processes. Both of these processes have certain disadvantages which make them less than ideal for high volume, high speed production of such strip products. For example, when injection molding such strip products, the effective rate of production is closely tied to the number of die cavities available. Moreover, dies for such products are relatively cumbersome and expensive. Additionally, the cycle time for such products tends to be relatively long because the strip products are flexible and very difficult to remove from the mold cavities and handle without damage until after they have cooled significantly.
Different but equally difficult problems are encountered when attempting to extrude such strip products. First, the use of the extruding process is generally limited to products of uniform cross section throughout their length. Secondly, it is very difficult to handle the extruded product and move it through the necessary cooling bath without deforming it and rendering it unsuitable for use. In addition to the above, the end shapes and contours of extruded products are limited to what can be accomplished by simple cutting operations.